Which type of antenna is known to radiate signals equally from all horizontal directions?

The antenna that radiates signals equally from all horizontal directions is the vertical 1/4 wave antenna. This type of antenna is designed to be a quarter of the wavelength of the frequency it is operating at, and it achieves an omnidirectional radiation pattern in the horizontal plane. This means that it can effectively transmit and receive signals from all directions at the same power level, which is particularly useful in applications where coverage in all directions is required.

When analyzing other types of antennas mentioned, the dipole antenna also has an omnidirectional pattern but is generally considered in a horizontal orientation. The Yagi-Uda antenna, on the other hand, is highly directional, focusing its signal in a specific direction, which enhances gain and range in that direction but does not radiate evenly across all horizontal angles. Similarly, the log-periodic antenna is designed to operate effectively over a range of frequencies but also has a directional pattern, offering strength in certain directions rather than being omnidirectional.